The invention relates to an apparatus and method for identifying foreign objects in an inductive charging system having a charging unit and having a vehicle for inductive charging, in which the charging unit includes a primary coil, and the vehicle includes a secondary coil in order to transmit electrical power from the primary coil to the secondary coil during a charging operation.
Electric and hybrid vehicles can usually be charged with an external charging unit by use of a cable connection. Charging without a cable, which can be implemented by inductive charging methods, is more convenient. Inductive transmission systems are known from the prior art, see for example GB 2 347 801 A1. The induction charging apparatus consists of a charging unit external to the vehicle having a primary coil and a vehicle unit having a secondary coil. With inductive charging, the two coils are spatially opposite one another and form a transmission region in which the electromagnetic transmission field is substantially located.
In addition, modern electric and hybrid vehicles have various types of driver assistance systems. These are complex electronic systems which support the vehicle user when operating the vehicle. Camera-based parking aids or lane guidance aids are cited as an example.
It is an object of the invention to provide an improved apparatus having a charging unit and having a vehicle for inductive charging.
According to the invention, the vehicle includes a camera system and a camera control unit. The camera system captures at least one image of the charging unit when approaching a charging station, at the beginning of a charging operation and/or during a charging operation. The camera control unit digitally processes the at least one captured image in order to detect a foreign body located on the charging unit.
Here, a charging operation is understood to be particularly the time period during which a transmission of electrical power takes place from the charging unit to the vehicle.
The term “approaching a charging station” encompasses an operation in which the vehicle assumes a specific parking position in spatial relationship to the charging unit in order to carry out a charging operation. This can also be supported by driver assistance systems such as a parking aid.
Without restricting generality, objects of all kinds, in particular however metallic objects, which are located in the transmission region during a charging operation, are described as foreign bodies. If an object comes to lie e.g. on the charging unit, which means that this object is also located in the transmission region, then this object can be detected by the captured image. The camera control unit determines the existence of a foreign body in the transmission region using digital image processing techniques based on the captured image.
According to a preferred embodiment of the invention, the charging unit includes a charging control device which controls the primary coil. At least one unidirectional data connection can be established from the camera control unit to the charging control device.
It is advantageous if the camera control unit generates a detection signal when a foreign body is detected, and the detection signal can be transmitted from the camera control unit to the charging control device by way of the established data connection.
When the detection signal is received from the camera control unit, the charging control device interrupts or reduces the transmission of power from the primary coil to the secondary coil.
This means that when a foreign body is detected, the apparatus suppresses or reduces the transmitted power so that the foreign body is subjected to a weakened transmission field or is no longer subjected to a transmission field. For this purpose, the charging control device receives the detection signal of the camera control unit and, as the driver of the primary coil, suppresses the transmission field located in the transmission region which emanates from the primary coil or reduces its field strength.
According to a preferred embodiment of the invention, the vehicle includes a communications unit to which the detection signal from the camera control unit can be transmitted and, when the detection signal is received by the communications unit, the communications unit outputs a discernible warning signal.
In this way, attention is drawn to the detected foreign body, for example, in a discernible manner for the vehicle user. This can, for example, be a visual display in the region of the driver's compartment or a discernible acoustic signal outside the vehicle. The discernible output can also contain a handling instruction, such as a request to clean the charging unit.
In order to detect a foreign body, a reference image of the charging unit without a foreign body on the charging unit or a foreign body in the transmission region is stored in the camera control unit. The camera control unit compares the at least one captured image with the reference image, wherein the deviation of the captured image from the reference image means the detection of a foreign body.
The detection of a foreign body is therefore based on a comparison of a captured actual image with the stored reference image. Preferably, the camera control unit carries out the image comparison using a segmenting method or using a pattern recognition method.
According to a further variant of the invention, the camera system and the camera control unit are components of a driver assistance system of the vehicle.
The invention is based on the considerations presented below.
Methods are known for electric vehicles which enable contactless, preferably inductive, charging of the motor vehicle on-board electrical system or of the storage device(s) contained therein.
As with inductive charging, the transmission of energy can be disrupted by metallic or electrically conducting materials between the two sides of the contactless transmission, measures must therefore be taken to detect such objects or materials and ensure countermeasures such as an interruption of the energy transmission. This successfully avoids undesirable heating of the foreign body and possible negative consequences.
The monitoring methods known from the prior art are either inadequate, as an overheating of very small or thin-walled conductive materials, such as a small coin for example, is not detected reliably or not quickly enough. However, the elimination of any potential hazard due to overheating of foreign bodies has the highest priority. Monitoring methods have a high degree of complexity without synergies with the technical monitoring systems (e.g. driver assistance systems) present in the vehicle being usable. Such solutions are therefore cost and space-intensive, as additional hardware is required.
A measure to use driver assistance systems of a vehicle during inductive charging to identify foreign bodies is provided.
For example, a sensor for image processing techniques, (e.g. an optical sensor such as a mono camera or stereo camera) integrated within a driver assistance system can be used to detect foreign bodies during inductive charging. This means that when the object to be charged, that is to say the vehicle, approaches a primary coil, that is to say the energy source, the existing sensor is activated or becomes activated. Where appropriate, the activation takes place automatically when approaching within a spatial boundary or, alternatively, a function takes place by manual activation. This sensor has image processing capabilities and compares every captured actual image with a reference image stored in the vehicle. The reference image specifies how the primary unit without any foreign body must be characterized. If the actual image deviates from the reference image, it is concluded that contamination or a foreign body is located in the region of the primary coil and inductive charging is prevented and/or the user of the system is given an appropriate hazard warning with a corresponding handling recommendation (e.g. request to clean). The imaging method can also preferably be carried out stereoscopically or spatially in order to detect size, type and degree of risk of the contamination or of the foreign body.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.